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Discussion Starter #1
Hello everyone, I'm looking at getting a new set of tires for my 1980 CM400t, but after doing some internet searching and some searching on this forum I still have a couple questions. My main question is in regards to tubed vs. tubeless on the star shaped rims. I saw on some other forums that some have "tubeless tire applicable" stamped on the rim, but mine do not. Other people said that any of the star rims after 1979 can take tubeless. I just wanted to get some more input on this as the tires that came on my bike when I bought it are a tubeless one the rear and a tubed on the front. When I first got the bike the rear tire would only sometimes hold air and took it to a shop and they pulled a torn tube out, threw a valve stem in and put it back on without a tube. I've been riding it that way for the last two years (I don't ride super often so less than 2500 miles since I've had it.) and I have noticed that every 3 weeks or so the rear loses about 5-6psi. So my main question is whether or not to go tubeless as I think I would prefer that if possible, and then also was wondering about the 120/90 vs 120/80 vs 130/90 for the rear tire. The current one is 120/80.
 

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Discussion Starter #2 (Edited)
Well I ended up deciding on a set of tires to get and figured I would check for the ridge on the inside of them when I remove the old tire and if need be run to the store and get some tubes. So far I've got the rear tire mounted and back on the bike and I figure'd I'd post my experience for those that have the same questions I had. I went with the Kenda k761 dual sport tire set, because I wanted something that would be a little better for the occasional rough dirt road and these are advertised as 80% road 20% off-road. They don't come in 120/90-16 or 100/90-18 so I went with 130/90-16 on the rear and 110/80-18 for the front. The difference in circumference between a 100/90-18 and a 110/80 was, according to my math pretty small and so it shouldn't affect my speedo readings much. I also calculated that at freeway speeds (around 75mph) the 130/90 on the rear should give me an extra 5ish mph at a given rpm. I won't be able to get to the front tire until next Saturday, but I've got the rear done. I've only ever changed tires by hand once before and the kenda k761 kicked my butt. It was just too stiff for me so I took it to pep boys to get the last 15in of bead over the rim. The rim does have a ridge to hold in the bead so I stuck with tubeless. The valve hole is very small and won't take normal pop-in valve stems so I had to order these on amazon.
Amazon.com: Circuit Performance VS33 Shorty Black Bolt-in Valve Stems (Set of 4): Automotive
To help get a better seal I cut the rubber gaskets so they were only the larger diameter (essentially a rubber washer now) and also put a little bit of of RTV silicone in there as well. (I'll update if I notice any leaks. I had read that with the 130/90 on the rear that the drum brake rod would need to be mounted outside of its bracket to clear the tire but I found it was not necessary and there is still a gap large enough so that the tire won't rub. I had also read that the chain guard would need to be modified, but I don't have a chain guard so I can't report on that. I don't believe there will be any issues with the front tire, but I will report about that and post some pics once I get it done.
 

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I just put Dunlop D404 on the front and rear - Revzilla.com had best price and even price matched.
 

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Well I ended up deciding on a set of tires to get and figured I would check for the ridge on the inside of them when I remove the old tire and if need be run to the store and get some tubes. So far I've got the rear tire mounted and back on the bike and I figure'd I'd post my experience for those that have the same questions I had. I went with the Kenda k761 dual sport tire set, because I wanted something that would be a little better for the occasional rough dirt road and these are advertised as 80% road 20% off-road. They don't come in 120/90-16 or 100/90-18 so I went with 130/90-16 on the rear and 110/80-18 for the front. The difference in circumference between a 100/90-18 and a 110/80 was, according to my math pretty small and so it shouldn't affect my speedo readings much. I also calculated that at freeway speeds (around 75mph) the 130/90 on the rear should give me an extra 5ish mph at a given rpm. I won't be able to get to the front tire until next Saturday, but I've got the rear done. I've only ever changed tires by hand once before and the kenda k761 kicked my butt. It was just too stiff for me so I took it to pep boys to get the last 15in of bead over the rim. The rim does have a ridge to hold in the bead so I stuck with tubeless. The valve hole is very small and won't take normal pop-in valve stems so I had to order these on amazon.
Amazon.com: Circuit Performance VS33 Shorty Black Bolt-in Valve Stems (Set of 4): Automotive
To help get a better seal I cut the rubber gaskets so they were only the larger diameter (essentially a rubber washer now) and also put a little bit of of RTV silicone in there as well. (I'll update if I notice any leaks. I had read that with the 130/90 on the rear that the drum brake rod would need to be mounted outside of its bracket to clear the tire but I found it was not necessary and there is still a gap large enough so that the tire won't rub. I had also read that the chain guard would need to be modified, but I don't have a chain guard so I can't report on that. I don't believe there will be any issues with the front tire, but I will report about that and post some pics once I get it done.
How is this working out for you? I've been going kind of crazy trying to find some duel sport tires for my '81 CM400T. I've been contemplating bumping up to 17 and 19 inch rims just to make it easier.
 
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